Ba-133 Neutron Capture Cross Section - Thermal & Excited States

In summary: E14 n/s/cmE2)?In summary, the conversation is about the thermal neutron capture cross sections for Ba-133, both in ground and excited states. The CRC Handbook provides a value of 4 barns, but the accuracy is being verified. The conversation then discusses the production of Ba-133 sources from enriched Ba-132 in a reactor, and the challenges involved due to the high cross section of Ba-132. The conversation also explores alternative isotopes with lower energy gammas and suitable half-lives for industrial gaging applications. The estimated time and cost for obtaining 100 mCi of Ba-133 from a
  • #1
GammaScanner
10
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Anybody have good values and a source for thermal neutron capture cross section for Ba-133, both ground and excited states? CRC Handbook gives 4 barns, but wanted to verify it. Thanks.
 
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  • #3
vanesch said:

Thanks! Good table. Cross sections for all the energies is a plus. Was looking at making some 100 mCi Ba-133 sources from enriched Ba-132 in reactor. But with Ba-132 at about 9 barns you don't make much, and with Ba-133 not much smaller at 4 barns, you lose a lot of the Ba-133 you do make. Takes a LOT of neutrons. Thanks again. - Ed
 
  • #4
GammaScanner said:
Thanks! Good table. Cross sections for all the energies is a plus. Was looking at making some 100 mCi Ba-133 sources from enriched Ba-132 in reactor. But with Ba-132 at about 9 barns you don't make much, and with Ba-133 not much smaller at 4 barns, you lose a lot of the Ba-133 you do make. Takes a LOT of neutrons. Thanks again. - Ed

Mmm, I would say that you still have the difference in nucleus densities:

You will reach equilibrium when you "burn" as much Ba-133 as you make, so you will reach equilibrium when:

flux x N(Ba-132) x 9 barn = flux x N(Ba-133) x 4 barn or

N(Ba-133) = 9/4 N(Ba-132)

In other words, unless you had the ambition to turn ALL of your Ba-132 into Ba-133, if you want just trace amounts, that should still be ok.

Or still in other words, if there are many more Ba-132 around than Ba-133, the probability for a neutron to be captured by the Ba-132 is still way higher than the probability for it to destroy a Ba-133, so you should win by neutron irradiation.
 
  • #5
If you're specifically trying to make Ba-133, that may not be the way to go. From the Radiological Health Handbook, the primary method of Ba-133 production is a Cs133(p,n)Ba133 reaction. If you just want to make something in the reactor, use something with a large cross section.
 
  • #6
vanesch said:
Or still in other words, if there are many more Ba-132 around than Ba-133, the probability for a neutron to be captured by the Ba-132 is still way higher than the probability for it to destroy a Ba-133, so you should win by neutron irradiation.

That's the thing I love about this stuff - scientific notation. The equilibrium ratio 9 to 4, is way more to us, but when we're talking 1.2 10E20 atoms of Ba-132 (in 100 mg Barium carbonate enriched to 40%, natural Barium has only .1% atoms of Ba-132) that gets us to 2.7 10E20 which just doesn't seem to be way more with all those zeros. :smile:

The folks at MURR (Missouri U Research Reactor) estimated it would take 5 weeks of irradiation in their hi flux neutron nook (4 10E14 n/s/cmE2) to get 100 mCi of Ba-133 from our 100 mg starting sample, at a cost on the order of $100,000 (if we could get the time, doubtful). And the cost of barium enriched in Ba-132 at $90 per mg was nothing to sneeze at either (not being a national lab). Doubling the amount of Ba-132 would cut the time in half (increasing Ba-132 cost from $9,000 to $18,000 though), but I had some volume constraints for the source size.

I can see why all the commercial isotope vendors seem to have 10mCi Ba-133 as an upper limit of activity. What's driving this is an industrial gaging application where I need a source of modest energy gammas. Cs-137 @ 662 KeV is way too high, Co-57 @ 122/136 KeV is fine, but the half life of 270 days is a nuisance in a machine that might be used for 20 years. Ba-133 with gammas ~ 300 KeV was a bit higher in energy than wanted, but the 10.5 year half life was useful.

Looks like I'll be sticking to Co-57, but it's interesting to look for other isotopes with low energy gammas, with a half life long enough to be useful, but short enough to get decent activity from a small volume.

For example, Rh-101 has 3.3 year half life and plentiful gammas @ 127 KeV and 198 KeV. But it doesn't look like it could be produced in a reactor (other than as a fission product). However, it might be made in an accelerator from Ru-100 + p -> Rh-101, but then Rh-101 + p -> Pd-102 which is stable + p -> Ag-103, etc. etc. and tables of proton capture seem not very comprehensive, for a reason I'm sure.
 
  • #7
GammaScanner said:
That's the thing I love about this stuff - scientific notation. The equilibrium ratio 9 to 4, is way more to us, but when we're talking 1.2 10E20 atoms of Ba-132 (in 100 mg Barium carbonate enriched to 40%, natural Barium has only .1% atoms of Ba-132) that gets us to 2.7 10E20 which just doesn't seem to be way more with all those zeros. :smile:

The folks at MURR (Missouri U Research Reactor) estimated it would take 5 weeks of irradiation in their hi flux neutron nook (4 10E14 n/s/cmE2) to get 100 mCi of Ba-133 from our 100 mg starting sample, at a cost on the order of $100,000 (if we could get the time, doubtful).

Mmm. I have slightly different numbers:
100 mg Ba with 40% of Ba-132 gives me 1.8E20 Ba-132 atoms

An activity of 100 mCi (3.7E9 Bq) of Ba-133 with a half-life of 10.52 years (3.32E8 seconds) gives me 1.77E18 atoms of Ba-133 that you want to obtain.

Now, irradiating 1.8E20 atoms of Ba-132 at a cross section of 4 barn with a flux of 4E14, will give me a needed time (not including capture by Ba-133):

time = 1.8E18 / {4E14 x 1.8E20 x 4E-24}= 6.1E6 seconds, or 71 days.

So how did they get to 5 weeks ? I find 10 weeks (sundays included).

Did I make a stupid mistake somewhere ?
 
  • #8
vanesch said:
Mmm. I have slightly different numbers:
100 mg Ba with 40% of Ba-132 gives me 1.8E20 Ba-132 atoms

An activity of 100 mCi (3.7E9 Bq) of Ba-133 with a half-life of 10.52 years (3.32E8 seconds) gives me 1.77E18 atoms of Ba-133 that you want to obtain.

Now, irradiating 1.8E20 atoms of Ba-132 at a cross section of 4 barn with a flux of 4E14, will give me a needed time (not including capture by Ba-133):

time = 1.8E18 / {4E14 x 1.8E20 x 4E-24}= 6.1E6 seconds, or 71 days.

So how did they get to 5 weeks ? I find 10 weeks (sundays included).

Raw material is barium carbonate, BaCO3, 196g/mole hence the 1.2E20 atoms of Ba-132, which makes it even longer. 1.77E18 of Ba-133 is what I had.

Cross section for Ba-132 is 9 barns which would give the 5 weeks (they run 6.5 days a week from what I understand), not counting the conversion of Ba-133 to Ba-134 which I'd think would be significant
 
  • #9
GammaScanner said:
Raw material is barium carbonate, BaCO3, 196g/mole hence the 1.2E20 atoms of Ba-132, which makes it even longer. 1.77E18 of Ba-133 is what I had.

Cross section for Ba-132 is 9 barns which would give the 5 weeks (they run 6.5 days a week from what I understand), not counting the conversion of Ba-133 to Ba-134 which I'd think would be significant

Uh, yes, *9* barn. I took erroneously the *4* barn of Ba-133 :redface:
 

Related to Ba-133 Neutron Capture Cross Section - Thermal & Excited States

What is the significance of Ba-133 neutron capture cross section?

The neutron capture cross section of an element is a measure of its ability to capture neutrons and form new isotopes. In the case of Ba-133, its cross section is important for understanding the behavior of this isotope in nuclear reactors and other nuclear applications.

What is the difference between thermal and excited states in Ba-133 neutron capture cross section?

The thermal state refers to the energy level of the neutrons being absorbed, which is typically around 0.025 eV. Excited states, on the other hand, refer to higher energy levels where neutrons may have energies of 1 eV or more. The cross section for neutron capture in these excited states may be different from the thermal cross section.

How is the Ba-133 neutron capture cross section determined?

The cross section is determined through experimental measurements using neutron sources and detectors. These experiments involve bombarding Ba-133 with neutrons of different energies and measuring the resulting neutron capture rate. The data is then analyzed to determine the cross section at various energy levels.

What factors can affect the Ba-133 neutron capture cross section?

The cross section can be influenced by factors such as temperature, energy of the neutrons, and the presence of other elements or isotopes. Additionally, the nuclear structure of Ba-133 can also play a role in determining the cross section.

How does the Ba-133 neutron capture cross section impact nuclear applications?

The cross section of Ba-133 is important for understanding the behavior of this isotope in nuclear reactors and other nuclear applications. It can affect the stability and efficiency of nuclear reactions, as well as the production of other isotopes through neutron capture. Therefore, a thorough understanding of the Ba-133 cross section is crucial for safe and efficient operation of nuclear systems.

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